Apparatus for interoffice trunk-lines.



No. 636,277. Patented Nov. 7, I899.

" F. H. MCBERTY.

APPARATUS FOR INTERDFFICE TRUNK LINES.

(Application filed' Sept. 25, 1896.)

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' UNITED STATES PATENT Enron.

FRANK R. MOBERTY, OF DOWNERS GROVE, ILLINOIS, ASSIGNOR TO THE IVESTERN ELECTRIC COMPANY, OF CHICAGO, ILLINOIS.

APPARATUS FOR INTEROFFICE TRUNK-LLINESI SPECIFICATION forming part of Letters Patent No. 636,277, dated November 7, 1899.

Application filed September 25, 1896. Serial No. 606,947. (No model.)

To aZZ whom it may concern.-

Be it known that I, FRANK R. MCBERTY, a citizen of the United States, residing at Downers Grove, in the county of Du Page and State of Illinois, have invented a certain new and useful Improvement in Apparatus for Interoffice Trunk-Lines, (Case No. 47,) of which the following is a full, clear, concise, and exact description, reference being had to the accompanying drawing, forming a part of this specification.

This invention concerns the transmission of signals in the operation of connecting and disconnecting two subscribers lines through the medium of an interoffice trunk-line.

In effecting connection between different subscribers lines by means of a trunk-line, it is common for the operator who receives the initial call to perform all necessary acts of bringing the subscribers into communication, excepting that of connecting the distant terminal of the trunk-line with the sub scribers line at the correspondent station, this step being of course performed by another operator. It is usual in such trunk-lines to provide aclearing-out annunciator before the operator who completes the connection, who is commonly designated the receivingoperator, can signify a call for the disconnection of the trunk-line from the subscribers line.

The object of the present invention'is to prevent the operation of this clearing-out annunciator in the trunk-line by the call-signal sent by the call-initiating operator to the called subscriber. Thatis accomplished by providing a device in connection with the clearing-out annunciator of the trunk-line for preventing its operation, the device being controlled or setinto operation by the callingkey of the call-originating operator.

The following form of theinvention is suitable for use under most conditions: The clearing-out annunciator at the receiving-station of the trunk-line may be connected in the trunk-line circuit in the usual way. About this clearing-out annunciator a shunt or short circuiting wire is provided, extending to the other terminal of the trunk-line and completed there through the agency of special contacts on the operators calling-key, operative only during the act of calling. This shunt-circuit may, if desired, be formed in part of a special conductor terminating in the plug of the originating or supervising operator, which is designed for insertion into the spring-jackusually forming the terminal of the trunk-line.

The attached drawing illustrates this form of the invention. It shows two substations terminating in springjacks and connected with annunciators in two different switchboards, a trunk-line extending between the two boards, and a pair of. plugs and their plug-circuit at one of the boards for making connection between a line and the trunk-line.

The subscribers apparatus may be of the usual type, consisting of a call-bell a, a generator a of alternating calling-current, a receiving-telephone a ,a transmitting-telephone of, and a switch for closing the circuit through the telephones during the use of the line.

These appliances are connected by the lineconductors 1 and 2 with a spring-jack b, and with an annunciator c at the switchboard. The line from station A terminates in switchboard e; that from station A is served at another switchboard f. Between these switchboards extends a trunk-line 3 4, which ends in a spring-jack gin the switchboard e, and which is furnished with a terminal plug h in the switchboard f. At the switchboard 6 pairs of plugs 2' and 11 are provided, with their plug-circuit 5 6. Associated with this circuit are a calling-key kfor connecting a generator Z of calling-current with the plug 2', a listening-key m for connecting the operators telephone n with the plug-circuit, andaclearing-out annunciator0,permanently connected in the bridge of the plug-circuit.

The trunk-line includes at the switchboard f an annunciatorp, which may be shunted by a non-inductive resistance-coil to eliminate its impedance to telephonic currents from the circuit.

In the present invention a wire 7 is led from one conductor 3 of the trunk-line intermediate of the annunciator and the terminal plug of the line to a contact-piece q in the trunkline jack g. The plug 2', which is designed for insertion into this jack, is furnished with a contact-sleeve a in position to register with the ring q when the plug is inserted in the springjack. This contact-piece 1' forms the terminal of a conductor 8, adapted to be brought into connection with the strand 5 of the plugcircuit. Its continuity is controlled by the switch-spring 7t and its anvil of the calling-key 70, which are brought into contact when the key is depressed to send a call-signal. Thus when the plug t" is in the trunkline jack 9 the depression of plunger-key 70 connects the generator Zof signaling-current with the trunk-line and at the same time closes the short-circuit about the clearing-out annunciator in the trunk-line.

Assume for the purpose of tracing the operation of the mechanism that the subscriber at station A requires a connection with station A. The subscriber causes the display of his line-annunciator c by the usual process of operating his calling-generator 04 Responding to the call,the operator at the switchboard 6 inserts plug i into the spring-jack b of the calling-line, and having learned the subscribers order inserts plug t" into the trunk-line jack g, at the same time communicating an order to the operator at switchboard f in any suitable way to connect that trunk-line with the line to station A. The latter operator performs this work in accordance with the instruction. The supervising operator at board 8 then manipulates callingkey It and sends a call-signal to the substation A. to operate the bell a there. Since the act of depressing the key 7t" completes a shortcircuit about the, clearing-out annunciator p of the trunk-line, that instrument is not operated by the signaling-current flowing in the trunk-line. At the termination of conversation either subscriber may transmit a call for disconnection by operating his generator. The current thus created will find circuit to both clearing-out annunciators 0 andp, causing them both to display their indicators. Thereupon the operators at both switchboards c andfwill proceed to remove the connections uniting the lines, the first operator withdrawing plugs '1 and z" from spring-jacks b and g and the second withdrawing the terminal plug h from the spring-jack b of the line to station A. It will be understood that unless the clearing-out annunciator were rendered inoperative in some manner during the transmission of a call-signal from the switchboard c through the trunk-line the annunciator would become displayed during such signaling and would give a false signal to the receiving-operator. The use of this invention therefore obviates confusion in making connection in the switchboard and permits the receiving-operator to place complete dependence upon the annunciator 1) as a signal for disconnecting the trunk-line from the subscribers line.

I claim as new 1. The combination with two telephonelines and a trunk-line uniting them, of a clearing-out annunciator at one terminal of the trunk-line in connection therewith, an operators calling-key at the other terminal of the trunk-line for connecting a source of calling-current with the line, and a device adapted to prevent the operation of the clearing-out annunciator, said device being conr be operated therewith, adapted to bring the said device into action; as described.

3. The combination with two telephonelines, and a trunk-line uniting them, of a clearing-out annunciator at one terminal of the trunk-line and an operatorscalling-key at the other terminal thereof, electrical circu'it connections adapted to render the clearin g-out annunciator inoperative, and a switch connected with the said calling-key controlling the circuit connections,whereby the operation of the calling-key renders the clearingout annunciator irresponsive; as described.

4. The combination with two telephonelines terminating in diiferent switchboards, a trunk-line between the switchboards, and a plug-circuit at one of the switchboards for making connection between a line there and one terminal of the trunk-line, of a clearingout annunciator connected with the other terminal of the trunk-line, an operators callingkey in the plug-circuit for sending signalingcurrent over the trunk-line, circuit connections adapted to render the clearing-out annunciatorinoperative, a conductor associated with the plug-circuit adapted to form an extension of the said circuit connections when the plug-circuit is connected with the trunkline, and switch-contacts on the calling-key controlling the connections of the said conductors; whereby the clearing-out annunciator may be made irresponsive to calling-currents sent in the trunk-line, as described.

5. The combination with a telephone-line, a trunk-line and a plug-circuit united serially to form an extended telephone-circuit, of a ringing-key in the plug-circuit, a clearing-out annunciator in the trunk-line at the other terminal thereof, and circuit connections controlled by the ringing-key adapted to render the clearing-out annnnciator inopshort circuit of the clearing-out annuneiator 1o erative during the transmission of a callingclosed by the said calling-key in the act of current, as described. sending a signal in the line, as described.

6. The combination with a te1eph0ne-1ine,- In Witness whereof I hereunto subscribe my a trunk-line and a plug-circuit serially eonname this 13th day of August, A. D. 1896.

neeted to form an extended telephonecircuit, FRANK R. MOBERTY. of a calling-key in the plug-circuit, a. clear- Witnesses:

ing-out annnneiator at the other terminal of ELLA EDLER,

the trunk-line connected therewith, and a LOLA J. BRINKERHOFF. 

